This invention relates to pressurization systems for space craft and missiles. More particularly, a compressed high vapor pressure liquid pressurizes a propellant feed system or functions as a reference pressure for a control device.
The propellant expulsion system of a liquid fuel engine constitutes a significant portion of the weight and cost of that engine. The propellant expulsion system includes a storage chamber for the propellant, a mechanism for feeding the propellant to a combustion chamber and a means to introduce the propellant into the chamber. The liquid propellant is stored in containers and fed to the combustion chamber either by a pressurized gas or by a displacement piston or centrifugal pump.
U.S. Pat. Nos. 3,009,361 to McKinley and U.S. Pat. No. 3,672,165 to Baum, disclose the use of a pressurized inert gas, typically helium, to expel a liquid propellant to a combustion chamber. A large volume of highly pressurized gas is required to expel an effective volume of propellant. The pressurized gas is stored in thick walled metallic containers until required. These containers occupy a significant portion of the available space within the rocket and contribute a significant weight penalty.
Another method for feeding liquid propellant to a combustion chamber is disclosed in U.S. Pat. No. 4,901,525 to Beveridge et al. The patent discloses delivering pressurized liquid propellant to a turbo pump. The propellant is then combined with a small amount of liquid oxidant and ignited to drive the turbo pump. The turbo pump then delivers a propellant rich liquid to the combustion chamber at high pressure. This method avoids the necessity of thick walled tanks to store a pressurized expulsion gas, but the large number of turbo pumps increases the cost and complexity of the delivery system.
There exists, therefore, a need for a liquid propellant delivery system which does not suffer from the weight, space and complexity problems of the prior art systems.